fix(appstore): verify pdf worker in js/ instead of dist/

After updating @libresign/pdf-elements, the build no longer produces
dist/pdf.worker.min-*.mjs. The pdf worker is now bundled into js/ by
Vite (via the dynamic import in pdf-elements' ensureWorkerReady()).

Update verify-appstore-package to:
- Assert js/ exists (unconditional, needed for frontend assets)
- Find pdf.worker.min-*.mjs in js/ (where it now lives)
- Keep the dist/ conditional only to check the directory was copied
  when it was produced (e.g. local env with an old build artifact)

[skip ci]

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

Makefile

@@ -177,7 +177,8 @@ appstore:
 .PHONY: verify-appstore-package
 verify-appstore-package:
 	test -d $(appstore_sign_dir)/$(app_name)/css
+	test -d $(appstore_sign_dir)/$(app_name)/js
+	find $(appstore_sign_dir)/$(app_name)/js -maxdepth 1 -name 'pdf.worker.min-*.mjs' | grep -q .
 	if [ -d dist ]; then \
 		test -d $(appstore_sign_dir)/$(app_name)/dist; \
-		find $(appstore_sign_dir)/$(app_name)/dist -maxdepth 1 -name 'pdf.worker.min-*.mjs' | grep -q .; \
 	fi